The invention relates to an electrical switchgear unit, for example a circuit breaker, equipped with a motorized control performing closing and, possibly, opening and resetting of the circuit breaker mechanism.
In the document U.S. Pat. No. 3,171,920 an electrical circuit breaker of the molded case type equipped with an operating handle is described, on which circuit breaker a motorized module for driving the handle is assembled. The module comprises a motor driving an endless screw operating in conjunction with a nut fixedly secured to the handle. The motor is of AC type comprising a first winding serving the purpose of driving the rotor in a first direction and a second winding for driving in the opposite direction. A changeover switch enables one or the other of the windings to be connected selectively to an electrical power source by means of a first and a second circuit branch each comprising a control push-button. The motor and endless screw are fitted in a frame fixed to the circuit breaker case. A guiding system gives the screw a small degree of freedom in translation with respect to the frame and to the stator of the motor. Springs urge the screw to a middle position. To close the circuit breaker from an open position of the handle, the closing push-button is actuated and the motor is supplied in a first running direction so as to drive the handle at high speed to the closed position. On its path, the handle passes without stopping via a closing dead point position beyond which the toggle mechanism of the circuit breaker rocks abruptly to the closed position. The motor continues its movement, without stopping, until the nut reaches the end of travel. The screw, continuing to turn, performs a slight translation against the bias of the return springs and makes the changeover switch change position, cutting the power supply to the motor. To reset the circuit breaker, the opening push-button is actuated and the motor is supplied in the second running direction to drive the handle without stopping to a loaded position situated slightly beyond the open position. When the nut reaches an end-of-travel stop, further rotation of the motor causes a slight translation of the screw and makes the changeover switch change position, which cuts the power supply to the motor. By means of this complex device, it is ensured on the one hand that the handle duly reaches its end-of-travel positions, and on the other hand that the inertia of the motor can be absorbed when translation of the screw takes place. In the document U.S. Pat. No. 3,171,920 a slight variation of the above principle is presented.
In the document EP 0,802,549 there is described a removable module for motorized driving of a handle of an electrical switchgear unit, a circuit breaker or contactor. The module comprises a motor that drives an endless screw operating in conjunction with a slide rack fixedly secured to the handle of the electrical switchgear unit. The slide rack moves in translation between two end-of-travel positions without any intermediate stopping. The slide rack comprises a window in which the handle of an operating selector switch is inserted. When the slide rack approaches either one of its end-of-travel positions, the edge of the window drives the handle of the operating changeover switch and makes the changeover switch change position, opening the motor power supply circuit. This arrangement enables the motor to be controlled with a single control changeover switch.
In these devices, the closing time following a closing order is conditioned by the distance to be covered between the loaded position and the closing dead point position, which is non-modifiable constructive data of the switchgear unit mechanism. To reduce the closing time, powerful motors therefore have to be provided and the kinematic linkage transmitting the movement of the motor to the switchgear unit handle has to be optimized so as to minimize the energy dissipated when closing takes place. Consequently, performance is obtained at the price of large dimensions and high cost.
The object of the invention is therefore to remedy the shortcomings of the state of the art so as to propose an electrical switchgear unit equipped with a motorized operating module of low power and small dimensions enabling a short closing time to be obtained.
According to the invention, these objectives are achieved by means of an electrical switchgear unit comprising:
a pair of separable contact means comprising at least one movable contact means movable between a contact position and a separated position;
an opening and closing mechanism of the switchgear comprising:
a primary member movable in a closing direction from a loaded position to a closed position passing via an intermediate closing dead point position, the movable contact means being in the separated position when the primary member is in the loaded position,
an energy storage spring arranged in such a way that the primary member loads the storage spring when passing from the loaded position to the closing dead point position, and that the storage spring discharges driving the movable contact means to the contact position when the primary member passes beyond the closing dead point in the closing direction;
an electric motor controlled by control means;
an irreversible kinematic transmission system between the electric motor and the primary member, such that the electric motor can drive the primary member but the primary member can not drive the electric motor, the motor running in a closing direction to drive the primary member in the closing direction;
characterized in that the control means comprise means for detecting passage of the primary member via an indexed intermediate stopping position between the loaded position and the closing dead point position and for stopping the motor when the motor drives the primary member in the closing direction and the primary member reaches the indexed stopping position.
As the handle already covers a part of the travel between the loaded position and the closing dead point position before the closing order is given, the distance remaining to be covered after the closing order is smaller and requires less energy.
Preferably, the indexed stopping position is closer to the closing dead point position than to the loaded position.
According to one embodiment, the control means comprise an auxiliary switch changing state when the primary member passes via the indexed stopping position.
Advantageously, the control means comprise means for detecting the fact that the primary member is in the closed position whereas the motor is controlled to run in the closing direction, and for stopping the motor in this case. This detection can be performed for example by an auxiliary end-of-travel micro-contact. If the motor is a stepper motor, detection can be achieved by determining the position of the motor. According to another, particularly simple, reliable and compact alternative embodiment, the motor is a DC motor supplied by a supply current controlled by the control means, and the control means comprise means for detecting the fact that the intensity of the supply current remains higher than a preset threshold during a preset time whereas the motor is supplied to run in the closing direction, and for interrupting the power supply of the motor in this case.
Commanding opening of the circuit breaker in the phase preceding preparation for closing also has to be provided for. Thus:
the primary member is movable in an opening direction that is the reverse of the closing direction, from the closed position to the setting position, passing via an intermediate opening dead point position, the energy storage spring loading when passing from the closed position to the opening dead point position when the movable contact is in the contact position and discharging driving the movable contact means to the separated position when the primary member continues its movement in the opening direction beyond the opening dead point position;
the motor is mobile in an opening direction that is the reverse of the closing direction, to drive the primary member in the opening direction;
the control means comprise means for detecting the fact that the primary member, driven by the motor in the opening direction, passes via an indexed turning position, and for reversing the direction of rotation of the motor in this case.
According to one embodiment, the indexed turning position is the loaded position. The motor is a DC motor supplied by a supply current controlled by the control means, and the control means comprise means for detecting the fact that the intensity of the supply current of the motor remains higher than a preset threshold during a preset time whereas the motor is supplied to run in an opening direction that is the reverse of the closing direction, and for changing the direction of rotation of the motor in this case. The switchgear unit is then particularly simple and reliable, on account of the small number of sensors.
According to another embodiment, the indexed turning position is an intermediate position between the opening dead point position and the loaded position, closer to the opening dead point position than to the loaded position. The movement of the primary member in the opening direction, and therefore the time preceding reclosing, is then minimized.
Another feature of the invention relates to a process for operating an electrical switchgear unit comprising:
a pair of separable contact means, comprising at least one movable contact means movable between a contact position and a separated position;
an opening and closing mechanism of the switchgear unit, comprising:
a primary member movable in a closing direction from a loaded position to a closed position passing via an intermediate closing dead point position, the movable contact means being in the separated position when the primary member is in the loaded position,
an energy storage spring arranged in such a way that the primary member loads the storage spring when passing from the loaded position to the closing dead point position, and that the storage spring discharges driving the movable contact means to the contact position when the primary member passes beyond the closing dead point in the closing direction;
an electric motor controlled by control means, the motor running in a closing direction to drive the primary member in the closing direction;
process that comprises an opening procedure of the switchgear unit comprising: a preparing for closing stage, wherein the motor drives the primary member in the closing direction up to an indexed intermediate stopping position situated between the loaded position and the closing dead point position, and stops in the intermediate stopping position.
Advantageously, the opening procedure comprises in addition an opening stage preceding the preparing for closing stage and wherein the movable contact means is moved to the separated position and wherein the motor drives the primary member in an opening direction opposite to the closing direction up to an indexed turning position.
According to one embodiment, the indexed turning position is the loaded position.
To minimize the opening time, it is provided that the mechanism comprises in addition: a latching member and a trip latch. The latching member is movable between a latched position and an unlatched position, and is in the latched position when the movable contact means is in the contact position. The trip latch is operated by an actuator and performs latching of the latching member in the latched position, the storage spring tending to simultaneously drive the latching member from the latched position to the unlatched position and the movable contact means from the contact position to the separated position when the latch releases the latching member. With such a mechanism, it is provided that in the opening stage, the movable contact means is moved to the separated position by commanding the actuator which unlatches the latch to release the latching member. The opening time is thus minimized, and becomes independent from the power of the motor. However, the time required for an opening-closing cycle remains long, as the motor must move the primary member back to the resetting position before being able to order closing.
According to another embodiment, the indexed turning position is situated between the loaded position and an opening dead point position situated between the closing dead point position and the loaded position, the storage spring loading as it passes from the closed position to the opening dead point position when the movable contact is in the contact position and discharging driving the movable contact means to the separated position when the primary member continues its movement in the opening direction passing beyond the opening dead point to the indexed turning position. In this case, the response time to an opening order is longer and depends on the power of the motor. However, the opening-closing cycle time is then minimized as the movement of the primary member is minimized.
Preferably, it is provided that in response to a closing order subsequent to the opening order, the motor drives the primary member from the intermediate stopping position to the closed position.